Electrical patching equipment, which typically includes an array of jacks and patch cords, is widely used in a variety of different applications for selectively connecting and disconnecting electrical circuits. For example, electrical patching equipment is widely utilized to make selected circuit connections between data communications equipment and computers or other signal utilization equipment.
Jack constructions known prior to this invention typically have either one or two patch cord plug-receiving sockets and a number of contact elements which are in one position when no patch cord plug is plugged into an associated plug-receiving socket and which are shifted to a second position by plugging a plug into the plug-receiving socket. Prior patch cords typically comprise a cord or cable with a plug connected to one or both ends of the cable. The plug typically has a number of contacts which are connected to conductors in the cable and which are adapted to make contact with the contact elements in the jack when the plug is inserted into the jack.
Various patch cord plug and jack constructions are currently known such as the constructions described in the following U.S. Letters Patents: U.S. Pat. No. 3,665,129 which issued on May 23, 1972 to Jesse F. Lancaster, U.S. Pat. No. 3,714,385 which issued on Jan. 30, 1973 to C. T. Leverich, U.S. Pat. No. 3,222,471 which issued on Dec. 7, 1965 to R. A. Steinkamp, U.S. Pat. No. 3,627,942 which issued on Dec. 14, 1971 to C. F. Bobb, U.S. Pat. No. 3,158,422 which issued on Nov. 24, 1964 to C. J. Bowden et al, and U.S. Pat. No. 3,154,360 which issued to P. J. Plishner on Oct. 27, 1964.
Although various prior patch cord and jack assemblies, such as the ones described in the above-mentioned U.S. Pat. Nos. 3,665,129 and 3,714,385, operate satisfactorily, they have various drawbacks or shortcomings. For example, while the jacks described in U.S. Pat. Nos. 3,665,129 each have a multiplicity of normally closed contacts which can concomitantly be opened by selective insertion of a single patch cord plug to conveniently and quickly patch multi-terminal circuits into and out of a patch field, they have no provision for monitoring, checking or measuring electrical conditions without breaking the normal through circuit connections which are established by the normally closed jack contacts. In addition, they have limited flexibility in making different circuit connections. Also, the jacks and patch cord plugs described in this patent contain numerous parts to make manufacture relatively expensive.
The plug and jack constructions described in U.S. Pat. No. 3,714,385 lack the advantageous multiple normal through circuit connections which are provided by the jacks in U.S. Pat. No. 3,665,129. Instead, they are only capable of providing normal through circuit connections between two terminals of one circuit and two terminals of another circuit. However, the jack and patch cord equipment in U.S. Pat. No. 3,714,385 does offer the advantage of permitting signals to be monitored without breaking the normal through circuit connections in the jack, but this can only be done by utilizing a specially constructed test probe plug which differs in construction from the regular patch cord plugs and by plugging the test probe plug into one of the two jack sockets which is normally used for patching equipment into and out of the patch field.